1. Field of the Invention
The present invention relates to a threaded closure assembly of a cap and neck of a bottle or container, which assembly provides high torque removal, and in particular, to an assembly of a cap on a neck where the cap has at least one locking rib and a thread on the neck which engages the rib. The assembly is desired to prevent cocking of the neck thread above the rib for a wide range of dimensions of the rib and of the threads on the neck and in the cap.
2. Description of the Prior Art
A problem with threaded closure caps is the tendency of the cap to loosen during shipping and handling as the material of which the cap is made starts to creep or relax. This tendency is not just a problem of the cap coming off the container neck on which it is initially received but also, this loosening prevents proper sealing of the cap which can lead to spoilage and/or spillage of the product inside the container.
In many of the previously proposed threaded closure cap assemblies, friction, which is generated between the normal mating of threads is relied upon to prevent the loosening tendency described above. However, this friction is usually insufficient to prevent loosening, especially when different thread tolerances between the container neck thread and the cap thread are encountered. Such a situation poses a problem when one thread, e.g., the container neck thread, is at a low tolerance and the other thread, the cap thread, is at a high tolerance and vice versa. When such adverse range of dimensional tolerances is encountered, there will not be sufficient friction created between the threads to prevent their loosening since space will exist between the threads.
Additionally, prior attempts to provide increased friction between the container neck thread and the cap thread by increasing the depth of one of the cap threads has not been fully effective. By this technique, increased friction is established by having the increased depth thread on the cap contact the neck of the container between revolutions of the container neck thread. This extra contact provides increased surface area contact to increase friction between the cap and the container neck and also forces the increased depth thread of the cap into the neck of the container.
However this technique has not proved to be effective for several different reasons. One problem is that the increased depth thread can cause deformation of the container neck which may be critical. Also, although increased friction is achieved by the contact of the increased depth thread with the container neck, friction which would normally exist between the other thread is diminished since the increased depth thread will tend to push the cap away from the container neck when the cap is tightened. This is especially true if the material of the container neck is relatively hard and does not deform properly.
Another problem with this method is that increased friction is not properly achieved when different tolerances of the cap and container neck threads are encountered. For instance, if the container neck thread tolerance is low and the cap thread tolerance is high, it is possible that the increased depth thread will not contact the container neck. Instead, it will jam into the container threads which will provide some additional friction but will also cause thread deformation which may prevent removal of the cap or prevent resealing of the cap on the container.
Another prior method for providing increased friction is the addition of an high torque removal thread with a smaller depth located slightly above the top thread of the cap. This additional high torque removal thread attempts to provide increased friction by jamming the container neck thread upward against the top of the top cap thread.
This method can be effective when nominal thread tolerances are encountered but loses its effectiveness in its application when different extremes of tolerances are encountered in both the cap and container threads. Specifically, mismatching of thread tolerances produces a situation known as thread cocking where the container neck thread cocks above the high torque removal thread.
As will be described in greater detail hereinafter, proper mating of the threads in any increased friction or high torque removal cap is essential. When using the method of providing an additional high torque removal thread or rib with a smaller depth, if the cap thread tolerance is high and the container thread tolerance is low, no jamming of the container thread is achieved since there will be too much space between the smaller depth rib and the top of the upper thread of the cap. Alternatively, if the cap thread tolerance is low and the container neck thread tolerance is high, the container thread will not seat properly within the cap thread to allow the smaller thread to jam the container neck thread in the proper manner.
Examples of previously proposed closure assemblies having high torque removal or anti-backoff characteristics are disclosed in the following U.S. Pat Nos:
______________________________________ U.S. Pat. No. PATENTEE ______________________________________ 3,295,708 Watten Jr. 3,696,957 Van Boarn 4,084,716 Bogert 4,084,717 King 4,193,509 Dunn, Jr. et al. 4,294,370 Tueppen 4,345,691 Burke 4,349,116 Luenser ______________________________________
The Luenser U.S. Pat. No. 4,349,116 discloses a closure cap having a secondary helical thread which will flex in response to a tightening torque.
As will be described in greater detail hereinafter, the anticocking high torque removal closure assembly of the present invention differs from the assemblies previously proposed by providing a rib (high torque removal thread) of smaller thread depth located above or below the top thread in a cap of the assembly. This rib provides increased friction by engaging a container neck thread at a point, which causes slight deformation of the front face of the container neck thread while providing the increased friction necessary to prevent backing off of the cap during shipping and handling.
Additionally, the closure assembly of the present invention is not defeated by different thread tolerances since the width of the top thread in the cap of the assembly is chosen so that proper engagement of the rib with the front face of a container neck thread takes place without cocking of the neck thread above the rib.